Substrate support assembly with deposited surface features

ABSTRACT

An electrostatic chuck comprises a ceramic body comprising an embedded electrode and a first ceramic coating on a surface of the ceramic body, wherein the first ceramic coating fills pores in the ceramic body. The electrostatic chuck further comprises a second ceramic coating on the first ceramic coating and a plurality of elliptical mesas on the second ceramic coating, the plurality of elliptical mesas having rounded edges.

RELATED APPLICATIONS

The present patent application is a continuation of U.S. applicationSer. No. 16/007,977, filed Jun. 13, 2018, which is a continuationapplication of U.S. application Ser. No. 14/944,018, filed Nov. 17,2015, issued as U.S. Pat. No. 10,020,218 on Jul. 10, 2018.

TECHNICAL FIELD

Embodiments of the present invention relate, in general, to a substratesupport assembly such as an electrostatic chuck that has a plasmaresistant protective layer with deposited surface features.

BACKGROUND

In the semiconductor industry, devices are fabricated by a number ofmanufacturing processes producing structures of an ever-decreasing size.Some manufacturing processes such as plasma etch and plasma cleanprocesses expose a substrate support such as an electrostatic chuck(ESC) (e.g., an edge of ESC during wafer processing and the full ESCduring chamber cleaning) to a high-speed stream of plasma to etch orclean the substrate. The plasma may be highly corrosive, and may corrodeprocessing chambers and other surfaces that are exposed to the plasma.

An ESC typically has surface features that are created by placing apositive mask on a surface of the ESC and then bead blasting exposedportions of the ESC through the positive mask. The positive mask is amask that contains an exact copy of the pattern which is to remain onthe wafer. The bead blasting process causes sharp edges and cracking inthe ESC surface. Additionally, the spaces between formed surfacefeatures (referred to as valleys) have a high roughness that providestraps that trap particles and peaks that can break during thermalexpansion. The trapped particles and broken peaks can cause particlecontamination on the backsides of wafers that are held duringprocessing.

SUMMARY

In one embodiment, an electrostatic chuck includes a thermallyconductive base and a ceramic body bonded to the thermally conductivebase, the ceramic body having an embedded electrode. A protectiveceramic coating covers a surface of the ceramic body. Multiple depositedelliptical mesas are distributed over the surface of the ceramic body.The elliptical mesas each have rounded edges.

In one embodiment, a method of manufacturing an electrostatic chuckincludes polishing a surface of a ceramic body of the electrostaticchuck to produce a polished surface. The method further includesdepositing a protective ceramic coating onto the polished surface of theceramic body to produce a coated ceramic body. The method furtherincludes disposing a mask over the coated ceramic body, the maskcomprising a plurality of elliptical holes (e.g., circular holes). Themethod further includes depositing a ceramic material through theplurality of elliptical holes of the mask to form a plurality ofelliptical mesas on the coated ceramic body, wherein the plurality ofelliptical mesas (e.g., circular mesas) have rounded edges. The mask isthen removed, and the plurality of elliptical mesas are polished.

In one embodiment, a circular mask for the deposition of ellipticalmesas onto a surface of an electrostatic chuck includes a body having afirst diameter that is less than a second diameter of the electrostaticchuck onto which the mask is to be placed. The circular mask furtherincludes multiple elliptical through holes in the body, the ellipticalthrough holes having an aspect ratio of approximately 1:2 toapproximately 2:1. At least one of the elliptical holes has a flared topend and a flared bottom end, wherein the flared top end is to funnelparticles through the elliptical hole onto the electrostatic chuck toform an elliptical mesa on the electrostatic chuck, and wherein theflared bottom end prevents the elliptical mesa from contacting the mask.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

FIG. 1 depicts a sectional side view of one embodiment of a processingchamber;

FIG. 2A depicts a top plan view of an example pattern of ellipticalmesas on a surface of an electrostatic chuck;

FIG. 2B depicts vertical cross-sectional view of the electrostatic chuckof FIG. 2A;

FIGS. 3A-D illustrate side profiles of example mesas, in accordance withembodiments of the present invention;

FIG. 4 depicts a sectional side view of one embodiment of anelectrostatic chuck;

FIG. 5 illustrates one embodiment of a process for manufacturing anelectrostatic chuck;

FIGS. 6A-C illustrate the deposition of a ceramic material through amask to form circular mesas with rounded edges on a surface of anelectrostatic chuck; and

FIG. 7 illustrates a top view of a mask used to form mesas and a ring ona ceramic body of an electrostatic chuck, in accordance with oneembodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention provide a substrate supportassembly (e.g., an electrostatic chuck) having deposited mesas withrounded edges. Embodiments also provide a substrate support assemblyhaving a protective ceramic coating formed over a ceramic body of thesubstrate support assembly. The protective ceramic coating may provideplasma corrosion resistance for protection of the ceramic body. Themesas may be deposited over the protective ceramic coating, and may alsobe resistant to plasma corrosion.

In one embodiment, an electrostatic chuck includes a thermallyconductive base (e.g., a metal or metal alloy base) and a ceramic body(e.g., an electrostatic puck) bonded to the thermally conductive base. Aprotective ceramic coating that acts as a protective layer covers asurface of the ceramic body, and numerous elliptical (e.g., circular)mesas are disposed over the protective ceramic coating. In oneembodiment, the electrostatic chuck is manufactured by first depositingthe protective ceramic coating on the ceramic body and then depositingthe elliptical mesas onto the ceramic body through holes in a mask. Asused herein, the term mesa means a protrusion on a substrate that hassteep sides and a flat or gently sloped top surface.

Notably, the electrostatic chucks and other substrate supports describedin embodiments herein have mesas that are produced by depositing themesas through a negative mask. The negative mask is a mask that containsan exact opposite of the pattern which is to be formed on theelectrostatic chuck. In other words, the negative mask has voids wherefeatures are to be formed on the electrostatic chuck. In contrast, mesasare traditionally formed on the surfaces of electrostatic chucks by beadblasting a surface of the electrostatic chuck through a positive mask (amask that contains an exact copy of a pattern that is to be transferredonto the electrostatic chuck). Mesas formed through the bead blastingprocess have sharp edges that can chip and cause particle contaminationon the backside of wafers supported by the electrostatic chuck. However,mesas that are deposited in accordance with embodiments described hereinhave rounded edges (e.g., a top-hat profile) that are much less prone tochipping.

Additionally, the bead blasting process traditionally used to producemesas in electrostatic chucks causes the area (valleys) between theproduced mesas to have a high surface roughness. The high surfaceroughness can act as a trap for particles, which may then be releasedonto the backside of a supported wafer during processing. Moreover,local peaks in the rough surface of the valleys can crack and break offduring thermal cycling. This can act as an additional source of particlecontaminants. However, in embodiments described herein a surface of theelectrostatic puck is polished prior to deposition of the mesas.Accordingly, the valleys between deposited mesas have a very low surfaceroughness (e.g., around 4-10 micro-inches), further reducing backsideparticle contamination.

Electrostatic chucks described in embodiments herein further include ablanket protective ceramic coating that acts as a protective layer forthe electrostatic chucks. The protective ceramic coating covers asurface of the electrostatic chuck, and is deposited onto theelectrostatic chuck after the surface of the electrostatic chuck ispolished. The protective ceramic coating is very conformal, and hasapproximately the same surface roughness of the polished electrostaticchuck. The protective ceramic coating and the mesas that are depositedon the protective ceramic coating may each be a plasma resistantmaterial such as yttrium aluminum garnet (YAG). Thus, the electrostaticchuck, including the mesas formed on the electrostatic chuck, may beresistant to Chlorine, Fluorine and Hydrogen based plasmas.

FIG. 1 is a sectional view of one embodiment of a semiconductorprocessing chamber 100 having a substrate support assembly 148 disposedtherein. The substrate support assembly 148 includes an electrostaticchuck 150 with an electrostatic puck 166 that has deposited mesas withrounded edges, in accordance with embodiments described herein.

The processing chamber 100 includes a chamber body 102 and a lid 104that enclose an interior volume 106. The chamber body 102 may befabricated from aluminum, stainless steel or other suitable material.The chamber body 102 generally includes sidewalls 108 and a bottom 110.An outer liner 116 may be disposed adjacent the side walls 108 toprotect the chamber body 102. The outer liner 116 may be fabricatedand/or coated with a plasma or halogen-containing gas resistantmaterial. In one embodiment, the outer liner 116 is fabricated fromaluminum oxide. In another embodiment, the outer liner 116 is fabricatedfrom or coated with yttria, yttrium alloy or an oxide thereof.

An exhaust port 126 may be defined in the chamber body 102, and maycouple the interior volume 106 to a pump system 128. The pump system 128may include one or more pumps and throttle valves utilized to evacuateand regulate the pressure of the interior volume 106 of the processingchamber 100.

The lid 104 may be supported on the sidewall 108 of the chamber body102. The lid 104 may be opened to allow access to the interior volume106 of the processing chamber 100, and may provide a seal for theprocessing chamber 100 while closed. A gas panel 158 may be coupled tothe processing chamber 100 to provide process and/or cleaning gases tothe interior volume 106 through a gas distribution assembly 130 that ispart of the lid 104. Examples of processing gases that may be flowedinto the processing chamber including halogen-containing gas, such asC₂F₆, SF₆, SiCl₄, HBr, NF₃, CF₄, CHF₃, CH₂F₃, Cl₂ and SiF₄, amongothers, and other gases such as O₂, or N₂O. Notably, the processinggases may be used to generate Chlorine-based plasmas, Fluorine-basedplasmas and/or Hydrogen-based plasmas, which may be highly corrosive.The gas distribution assembly 130 may have multiple apertures 132 on thedownstream surface of the gas distribution assembly 130 to direct thegas flow to the surface of a substrate 144 (e.g., a wafer) supported bythe substrate support assembly 148. Additionally, or alternatively, thegas distribution assembly 130 can have a center hole where gases are fedthrough a ceramic gas nozzle.

The substrate support assembly 148 is disposed in the interior volume106 of the processing chamber 100 below the gas distribution assembly130. The substrate support assembly 148 holds the substrate 144 duringprocessing. An inner liner 118 may be coated on a periphery of thesubstrate support assembly 148. The inner liner 118 may be ahalogen-containing gas resist material such as those discussed withreference to the outer liner 116. In one embodiment, the inner liner 118may be fabricated from the same materials of the outer liner 116.

In one embodiment, the substrate support assembly 148 includes amounting plate 162 supporting a pedestal 152, and an electrostatic chuck150. The mounting plate 162 may be coupled to the bottom 110 of thechamber body 102 and includes passages for routing utilities (e.g.,fluids, power lines, sensor leads, etc.) to the thermally conductivebase 164 and the electrostatic puck 166. In one embodiment, theelectrostatic chuck 150 further includes a thermally conductive base 164bonded to an electrostatic puck 166 by a silicone bond 138.

The electrostatic puck 166 may be a ceramic body that includes one ormore clamping electrodes (also referred to as chucking electrodes) 180controlled by a chucking power source 182. In one embodiment, theelectrostatic puck 166 is composed of aluminum nitride (AlN) or aluminumoxide (Al₂O₃). The electrostatic puck 166 may alternatively be composedof titanium oxide (TiO), titanium nitride (TiN), silicon carbide (SiC),or the like. The electrode(s) 180 (or other electrode(s) disposed in theelectrostatic puck 166) may further be coupled to one or more radiofrequency (RF) power sources 184, 186 through a matching circuit 188 formaintaining a plasma formed from process and/or other gases within theprocessing chamber 100. The one or more RF power sources 184, 186 aregenerally capable of producing an RF signal having a frequency fromabout 50 kHz to about 3 GHz and a power of up to about 10,000 Watts.

An upper surface of the electrostatic puck 166 is covered by aprotective ceramic coating 136 that is deposited onto the electrostaticpuck 166. In one embodiment, the protective ceramic coating is aY₃Al₅O₁₂ (Yttrium Aluminum Garnet, YAG) coating. Alternatively, theprotective ceramic coating may be Al₂O₃, AlN, Y₂O₃ (yttria), or AlON(Aluminum Oxy Nitride). The upper surface of the electrostatic puck 166further includes multiple mesas and/or other surface features that havebeen deposited onto the upper surface. The mesas and/or other surfacefeatures may have been deposited onto the surface of the electrostaticpuck 166 before or after the protective ceramic coating 146 wasdeposited thereon.

The electrostatic puck 166 further includes one or more gas passages(e.g., holes drilled in the electrostatic puck 166). In operation, abackside gas (e.g., He) may be provided at controlled pressure into thegas passages to enhance heat transfer between the electrostatic puck 166and the substrate 144.

The thermally conductive base 164 may be a metal base composed of, forexample, aluminum or an aluminum alloy. Alternatively, the thermallyconductive base 164 may be fabricated by a composite of ceramic, such asan aluminum-silicon alloy infiltrated with SiC to match a thermalexpansion coefficient of the ceramic body. The thermally conductive base164 should provide good strength and durability as well as heat transferproperties. In one embodiment, the thermally conductive base 164 has athermal conductivity of over 200 Watts per meter Kelvin (W/m K).

The thermally conductive base 164 and/or electrostatic puck 166 mayinclude one or more embedded heating elements 176, embedded thermalisolators 174 and/or conduits 168, 170 to control a lateral temperatureprofile of the substrate support assembly 148. The conduits 168, 170 maybe fluidly coupled to a fluid source 172 that circulates a temperatureregulating fluid through the conduits 168, 170. The embedded thermalisolators 174 may be disposed between the conduits 168, 170 in oneembodiment. The one or more embedded heating elements 176 may beregulated by a heater power source 178. The conduits 168, 170 and one ormore embedded heating elements 176 may be utilized to control atemperature of the thermally conductive base 164, thereby heating and/orcooling the electrostatic puck 166 and the substrate 144 beingprocessed. The temperature of the electrostatic puck 166 and thethermally conductive base 164 may be monitored using a plurality oftemperature sensors 190, 192, which may be monitored using a controller195.

FIG. 2A depicts a top plan view of an example pattern of ellipticalmesas 202 on a surface 212 of an electrostatic puck 200. Only sixteenmesas are shown for illustration purposes. However, the surface of theelectrostatic puck 200 may have hundreds or thousands of mesas formedthereon. FIG. 2B depicts vertical cross-sectional view of theelectrostatic puck of FIG. 2A taken along a centerline 3-3 of FIG. 2A.The electrostatic puck 200 includes one or more embedded electrodes 250.The electrostatic puck 200 may be an uppermost component of anelectrostatic chuck, such as electrostatic chuck 150 of FIG. 1. Theelectrostatic puck 200 has a disc-like shape having an annular peripherythat may substantially match the shape and size of a supported substrate244 positioned thereon. In one embodiment, the electrostatic puck 200corresponds to electrostatic puck 166 of FIG. 1.

In the example shown in FIG. 2A, the elliptical mesas 202 are depictedas being positioned along concentric circles 204 and 206 on the surface212 of the electrostatic puck 200. However, any pattern of mesas 202distributed over the surface 212 of the electrostatic puck 200 ispossible. The elliptical mesas 202 in one embodiment are circular.Alternatively, the elliptical mesas 202 may be oval in shape or haveother elliptical shapes.

The mesas 202 are formed as individual pads having a thickness between2-200 microns (μm) and dimensions in the plan view (e.g., diameters)between 0.5 and 5 mm. In one embodiment, the mesas 202 have a thicknessbetween 2-20 microns and diameters of about 0.5-3 mm. In one embodiment,the mesas 202 have thicknesses of about 3-16 microns and diameters ofabout 0.5-2 mm. In one embodiment, the mesas have a thickness of about10 microns and a diameter of about 1 mm. In one embodiment, the mesashave a thickness of about 10-12 microns and a diameter of about 2 mm. Insome embodiments, the mesas have a uniform shape and size.Alternatively, various mesas may have different shapes and/or differentsizes. Sidewalls of the elliptical mesas 202 may be vertical or sloped.Notably, each of the mesas 202 has rounded edges where the mesas 202will contact the substrate 244. This may minimize chipping of the mesas202 and reduce particle contamination on a backside of the substrate244. Additionally, the rounded edges may reduce or eliminate scratchingof the backside of substrate 244 due to chucking. Alternatively, themesas 202 may have chamfered edges.

Some example side profiles of mesas 220 are illustrated in FIGS. 3A-3D.As shown, in each of the example side profiles of FIGS. 3A-3D the edgesof the mesas are rounded. The side profiles of FIGS. 3A-B are variationsof a top hat profile.

Referring back to FIGS. 2A-2B, the mesas 202 are deposited mesas thathave been formed by a deposition process that forms a dense, conformalceramic layer, such as ion assisted deposition (IAD). Deposition of themesas 202 is discussed with reference to FIG. 5. In the illustratedembodiment, the mesas 202 have been deposited directly onto the surface212 of the electrostatic puck 200 without first depositing a protectiveceramic coating on the surface 212. However, a protective ceramiccoating may also be deposited before or after deposition of theelliptical mesas 202. An average surface roughness of the mesas 202 maybe about 2-12 micro-inches. In one embodiment, an average surfaceroughness of the mesas 202 is about 4-8 micro-inches.

In one embodiment, the mesas 202 are formed of YAG. In one embodiment,the mesas a composed of an amorphous ceramic including yttrium, aluminumand oxygen (e.g., YAG in an amorphous form). The amorphous ceramic mayinclude at least 8% by weight yttrium. In one embodiment, the amorphousceramic includes about 8-20% by weight yttrium, 20-32% by weightaluminum and 60-70% by weight oxygen. In one embodiment, the amorphousceramic includes about 9-10% by weight yttrium, about 25-26% by weightaluminum, and about 65-66% by weight oxygen. In alternative embodiments,the mesas 202 may be Al₂O₂, AlN, Y₂O₃, or AlON.

The surface 212 of the electrostatic puck 200 further includes a raisedlip in the form of a ring 218 at an outer perimeter 220 of theelectrostatic puck 200. The ring 218 may have a thickness and a materialcomposition that are the same or approximately the same as the thicknessand the material composition of the elliptical mesas 202. The ring 218may have been formed by deposition at the same time that mesas 202 wereformed. The ring 218 may also have rounded edges where the ring 218contacts the substrate 244. Alternatively, the ring 218 may havechamfered edges, or may have edges that are neither rounded norchamfered. In one embodiment, an inner edge of the ring 218 is roundedand an outer edge of the ring 218 is not rounded.

Tops of the elliptical mesas 202 and ring 218 contact a backside ofsupported substrate 244. The elliptical mesas 202 minimize a contactarea of the backside of the substrate 244 with the surface 212 of theelectrostatic puck 200 and facilitate chucking and de-chuckingoperations. A gas such as He can also be pumped into an area between thesubstrate and the electrostatic chuck 200 to facilitate heat transferbetween the substrate 244 and the electrostatic chuck 200. The ring 218may act as a sealing ring that prevents the gas from escaping the spacebetween the electrostatic chuck 200 and substrate 244.

FIG. 4 illustrates a cross sectional side view of an electrostatic chuck400, in accordance with one embodiment. The electrostatic chuck 400includes a thermally conductive base 464 (e.g., a metal base) coupled toan electrostatic puck 402 by a bond 452 such as a silicone bond. Thebond 452 may be, for example, a polydimethyl siloxane (PDMS) bond. Theelectrostatic puck 402 may be a substantially disk shape dielectricceramic body with one or more embedded electrodes. The electrostaticpuck 402 may be a bulk sintered ceramic such as aluminum oxide (Al₂O₃),aluminum nitride (AlN), titanium oxide (TiO), titanium nitride (TiN),silicon carbide (SiC) and the like. The electrostatic puck 402 mayinclude one or more embedded electrodes 436 and/or resistive heatingelements 438 (e.g., an inner resistive heating element and an outerresistive heating element. A quartz ring 446, or other protective ring,may surround and cover portions of the electrostatic chuck 400. Asubstrate 444 may be lowered down over the electrostatic chuck 400 andbe held in place via electrostatic forces by providing a signal to theone or more electrodes 436.

Thermally conductive base 464 is configured to provide physical supportto the electrostatic puck 402. In some embodiments, thermally conductivebase 464 is also configured to provide temperature control. Thermallyconductive base 464 may be made from a thermally conductive material,for example a metal such as aluminum or stainless steel. Thermallyconductive base 464 may comprise one or more heat exchangers, forexample, an embedded heating element, fluid channels providing heatexchange by circulating cooling and heating fluids through the channels,or a combination thereof. In FIG. 1, thermally conductive base 464includes multiple fluid channels also referred to as conduits 470 (e.g.,an inner conduit and an outer conduit) through which fluids may beflowed to heat or cool thermally conductive base 464, electrostaticchuck 400, and the substrate 444 through thermal energy exchange betweenthe thermally conductive base 464 and other components of theelectrostatic chuck 400 and the substrate 444. The temperature ofthermally conductive base 464 may be monitored using a temperaturesensor 490.

In one embodiment, the electrostatic chuck 150 additionally includes aceramic coating 496 that fills in and/or covers defects in a surface ofthe electrostatic puck 402 such as micro cracks, pores, pinholes, andthe like. Ceramic coating 496 may be referred to as a cover ceramiccoating or blanket ceramic coating, and may cover an entire surface ofthe electrostatic puck 402. Alternatively, the electrostatic chuck 150may not include ceramic coating 496. In one embodiment, the ceramiccoating 496 is composed of a same ceramic as the electrostatic puck 402.Accordingly, if the electrostatic puck 402 is AlN, then the coverceramic coating 496 is also AlN. Alternatively, if the electrostaticpuck 402 is Al₂O₃, then the ceramic coating 496 is also Al₂O₃.Alternatively, the ceramic coating may be composed of a same material asa second ceramic coating 494 (discussed below). In one embodiment, theceramic coating 496 has a thickness of less than 1 micron up to tens ofmicrons.

The ceramic coating 496 may initially have a thickness of at least 5microns when deposited to fill pores that may have a depth of up toabout 5 microns or more. However, the ceramic coating 496 may bepolished down to a thickness 1 micron or less. In some instances, theceramic coating 496 may be substantially polished away, so that it onlyremains in the pores of the electrostatic puck 402 that it filled. Theceramic coating 496 may be polished to an average surface roughness (Ra)of 2-12 micro-inches. In one embodiment, the ceramic coating 496 ispolished to a surface roughness of about 4-8 micro-inches. If no coverceramic coating is used, then the surface of the electrostatic puck 402may be polished to the surface roughness of 2-12 micro-inches.

In one embodiment, the ceramic coating 496 (or electrostatic puck 402)is polished to an average surface roughness of approximately 4-8micro-inches. Lower surface roughness is desirable to minimize particlecontamination and seal grain boundaries. Generally, the lower thesurface roughness, the less particle contamination that occurs.Moreover, by sealing grain boundaries in ceramic coating 494 and/orelectrostatic puck 402, the ceramic coating 494 and/or electrostaticpuck 402 becomes more resistant to corrosion. However, the lower thesurface roughness, the greater the number of nucleation sites that arepresent for subsequent deposition of ceramic coating 494 and/or mesas492. Moreover, lowering the surface roughness reduces an adhesionstrength of subsequent coatings over the electrostatic puck 402.Accordingly, it was unexpectedly discovered that performance degradeswhen the surface of the ceramic coating 496 and/or electrostatic puck402 is polished to less than about 4 micro-inches.

Electrostatic chuck 400 additionally includes a ceramic coating 494,which in embodiments is a protective ceramic coating. The ceramiccoating 494 may be disposed over ceramic coating 496 or may be disposedover electrostatic puck 402 if no cover ceramic coating was deposited.Ceramic coating 494 protects electrostatic puck 402 from corrosivechemistries, such as hydrogen-based plasmas, chlorine-based plasmas andfluorine-based plasmas. Ceramic coating 494 may have a thickness of afew microns to hundreds of microns.

In one embodiment, the ceramic coating 494 has a thickness of about 5-30microns. The ceramic coating 494 may be a highly conformal coating, andmay have a surface roughness that substantially matches the surfaceroughness of the ceramic coating 496 and/or electrostatic puck 402. Ifthe ceramic coating 496 was deposited and polished, then the ceramiccoating 494 may be substantially free from pores, pinholes,micro-cracks, and so on. The ceramic coating 494 may be Al₂O₃, AlN,Y₂O₃, Y₃Al₅O₁₂ (YAG), and AlON. In one embodiment, the ceramic coating494 is amorphous YAG having at least 8% by weight yttrium. In oneembodiment, the ceramic coating 494 has a Vickers hardness (5 Kgf) ofabout 9 Giga Pascals (GPa). Additionally, the ceramic coating 494 in oneembodiment has a density of around 4.55 g/cm3, a flexural strength ofabout 280 MPa, a fracture toughness of about 2.0 MPa·M^(1/2), a YoungsModulus of about 160 MPa, a thermal expansion coefficient of about8.2×10⁻⁶/K (20˜900° C.), a thermal conductivity of about 12.9 W/mK, avolume resistivity of greater than 10¹⁴ Ω·cm at room temperature, and afriction coefficient of approximately 0.2-0.3.

As briefly mentioned above, the structure of the ceramic coating 494 andmesas 492 is at least partially dependent on a roughness of theelectrostatic puck 402 and/or ceramic coating 496 due to a number ofnucleation sites associated with the roughness. When the surfaceroughness of the electrostatic puck 402 and/or ceramic coating 496 arebelow about 3 micro-inches, the surface on which the ceramic coating 494is deposited has very many nucleation sites. This large number ofnucleation sites results in a completely amorphous structure. However,by depositing the ceramic coating 494 onto a surface having a surfaceroughness of about 4-8 micro-inches, the ceramic coating 494 grows or isdeposited as an amorphous structure with many vertical fibers ratherthan as a purely amorphous structure.

In one embodiment, mesas 492 and a ring 493 are deposited over theceramic coating 494. In such an embodiment, the mesas 492 may becomposed of the same material as the ceramic coating 494. Alternatively,the mesas 492 and ring 493 may be deposited prior to the ceramic coating494 (and thus may be underneath the ceramic coating 494). In such anembodiment, the mesas 492 and ring 493 may either be the same materialas the electrostatic puck 402 or the same material as the ceramiccoating 494. The mesas may be around 3-15 microns tall (about 10-15 inone embodiment) and about 0.5-3 mm in diameter in some embodiments.

If the electrostatic chuck 400 is to be refurbished after use, then thethickness of the ceramic coating 494 may be at least 20 microns inembodiments, and around 20-30 microns in one embodiment. To refurbishthe electrostatic chuck 400, the mesas 492 may be removed by grinding,and a portion of the ceramic coating 494 may additionally be removed bygrinding. The amount of material to be removed during grinding may bedependent on an amount of bow in a surface of the electrostatic chuck400. For example, if the mesas are 8 microns thick and there is 5microns of bow in the electrostatic chuck 400, then approximately 15microns may be removed from the surface of the electrostatic chuck 400to completely remove the mesas 492 and to remove the 5 micron bow. Athickness of at least 20 microns may ensure that the underlyingelectrostatic puck 402 is not ground during refurbishment inembodiments. Once the mesas and bow have been removed via grinding, anew ceramic coating may be applied over a remainder of the ceramiccoating 494, and new mesas 492 and/or other surface features may beformed over the new ceramic coating as described herein.

FIG. 5 illustrates one embodiment of a process 500 for manufacturing anelectrostatic chuck. Process 500 may be performed to manufacture any ofthe electrostatic chucks described in embodiments herein, such aselectrostatic chuck 400 of FIG. 4. At block 505 of process 500, aninitial ceramic coating (referred to as a cover ceramic coating) isdeposited onto a ceramic body of an electrostatic chuck to fill inpores, pinholes, micro-cracking, and so on in the ceramic body. Thecover ceramic coating may be formed of a same material as the ceramicbody. For example, both the ceramic body and the cover ceramic coatingmay be AlN or Al₂O₃. Alternatively, the cover ceramic coating may beformed of a same material as a subsequently deposited protective ceramiccoating. For example, both the cover ceramic coating and the protectiveceramic coating may be YAG, Y₂O₃, Al₂O₃, AlN or AlON.

In one embodiment, the cover ceramic coating is deposited via ionassisted deposition (IAD). Exemplary IAD methods include depositionprocesses which incorporate ion bombardment, such as evaporation (e.g.,activated reactive evaporation (ARE)) and sputtering in the presence ofion bombardment to form coatings as described herein. One example IADprocess is electron beam IAD (EB-IAD). Other conformal and densedeposition processes that may be used to deposit the cover ceramiccoating include low pressure plasma spray (LPPS), plasma spray physicalvapor deposition (PS-PVD), and plasma spray chemical vapor deposition(PS-CVD), chemical vapor deposition (CVD), physical vapor deposition(PVD), sputtering, or combinations thereof. Other conformal depositiontechniques may also be used.

If IAD is used to deposit the cover ceramic coating, the cover ceramiccoating is formed on the ceramic body by an accumulation of depositionmaterials in the presence of energetic particles such as ions. Thedeposition materials may include atoms, ions, radicals, and so on. Theenergetic particles may impinge and compact the thin film protectivelayer as it is formed. A material source provides a flux of depositionmaterials while an energetic particle source provides a flux of theenergetic particles, both of which impinge upon the ceramic bodythroughout the IAD process. The energetic particle source may be anoxygen or other ion source. The energetic particle source may alsoprovide other types of energetic particles such as inert radicals,neutron atoms, and nano-sized particles which come from particlegeneration sources (e.g., from plasma, reactive gases or from thematerial source that provide the deposition materials).

The material source (e.g., a target body) used to provide the depositionmaterials may be a bulk sintered ceramic corresponding to the sameceramic that the cover ceramic coating is to be composed of. Othertarget materials may also be used, such as powders, calcined powders,preformed material (e.g., formed by green body pressing or hotpressing), or a machined body (e.g., fused material).

IAD may utilize one or more plasmas or beams (e.g., electron beams) toprovide the material and energetic ion sources. Reactive species mayalso be provided during deposition of the plasma resistant coating. Inone embodiment, the energetic particles include at least one ofnon-reactive species (e.g., Ar) or reactive species (e.g., O). Infurther embodiments, reactive species such as CO and halogens (Cl, F,Br, etc.) may also be introduced during the formation of a plasmaresistant coating. With IAD processes, the energetic particles may becontrolled by the energetic ion (or other particle) source independentlyof other deposition parameters. According to the energy (e.g.,velocity), density and incident angle of the energetic ion flux,composition, structure, crystalline orientation and grain size of theceramic coating may be manipulated. Additional parameters that may beadjusted are working distance and angle of incidence.

Post coating heat treatment can be used to achieve improved coatingproperties. For example, it can be used to convert an amorphous coatingto a crystalline coating with higher erosion resistance. Another exampleis to improve the coating to substrate bonding strength by formation ofa reaction zone or transition layer.

The IAD deposited cover ceramic coating may have a relatively low filmstress (e.g., as compared to a film stress caused by plasma spraying orsputtering). The relatively low film stress may cause the ceramic bodyto remain very flat, with a curvature of less than about 50 microns overthe entire ceramic body for a body with a 12 inch diameter. The IADdeposited cover ceramic coating may additionally have a porosity that isless than 1%, and less than about 0.1% in some embodiments. Therefore,the IAD deposited cover ceramic coating is a dense structure.Additionally, the IAD deposited cover ceramic coating may have a lowcrack density and a high adhesion to the ceramic body.

The ceramic body may be the electrostatic puck described previously. Theceramic body may have undergone some processing, such as to form anembedded electrode and/or embedded heating elements. A lower surface ofthe ceramic body may be bonded to a thermally conductive base by asilicone bond. In an alternative embodiment, the operation of block 505is not performed.

At block 510, a surface of the ceramic body is polished to produce apolished surface having a surface roughness of about 2-12 micro-inches.In one embodiment, the surface of the ceramic body is polished to anaverage surface roughness (Ra) of about 4-8 micro-inches. The polishingmay reduce the initial ceramic coating and/or may almost completelyremove the initial ceramic coating except for a portion of the initialceramic coating that filled in the pores, pinholes, etc.

At block 520, a ceramic coating (e.g., a protective ceramic coating) isdeposited or grown onto the polished surface of the ceramic body (e.g.,over the initial ceramic coating). In one embodiment, the ceramiccoating is YAG, Y₂O₃, Al₂O₃, AlN or AlON. The ceramic coating may be aconformal coating that may be deposited by any of the depositiontechniques discussed with reference to block 505. For example, theceramic coating may be deposited by performing IAD such as EB-IAD. Theceramic coating may be deposited to a thickness of up to hundreds ofmicrons. In one embodiment, the ceramic coating is deposited to athickness of approximately 5-30 microns. In one embodiment, the ceramiccoating is deposited to a thickness of about 5-10 microns. In oneembodiment, the ceramic coating is deposited to a thickness of about20-30 microns.

At block 520, a negative mask is disposed over the coated ceramic body.The negative mask may be a circular mask with a disk-like shape. Thenegative mask may have a diameter that is slightly less than a diameterof the ceramic body. The negative mask may additionally include manythrough holes, where each through hole is a negative of a mesa that isto be formed on the ceramic body. The negative mask is discussed ingreater detail below with reference to FIGS. 6A-C and FIG. 7. In oneembodiment, the negative mask is bonded to the ceramic body by anadhesive (e.g., is glued to the ceramic body). Alternatively, thenegative mask may be held in place over the ceramic body by a mechanicalholder.

At block 525, a ceramic material is deposited through the holes of thenegative mask to form mesas with rounded edges. Additionally, theceramic material may be deposited on an exposed portion of the ceramicbody at the perimeter of the ceramic body to form a ring thereon. Thering may be formed at the same time as the mesas. The mesas and ring maybe conformal and dense, and may be deposited by any of the depositiontechniques discussed with reference to block 505 above. For example, themesas and ring may be deposited using IAD such as EB-IAD.

In one embodiment, the holes in the mask have flared top ends and flaredbottom ends. The flared top ends act as a funnel to funnel material intothe holes and increase a deposition rate. The flared bottom ends inconjunction with an aspect ratio of the holes (e.g., an aspect ratio of1:2 to 2:1) may function to control a shape of the deposited mesasand/or the deposited ring. For example, the aspect ratio combined withthe flared bottom ends may cause the deposited mesas to have roundededges and/or a top hat profile. Moreover, the flared bottom ends preventthe mesas from contacting the walls of the holes. This may prevent themesas from bonding to the mask and bonding the mask to the ceramic body.

In one embodiment, the inner edge of the ring is rounded but the outeredge of the ring is not rounded. This may be because a shape of thenegative mask may cause the inner edge of the ring to become roundedduring deposition, but there may be no portion of the mask at the outeredge of the ring to control a deposited shape. Alternatively, the edgesof the ring may not be rounded.

At block 530, the mask is removed from the ceramic body. At block 535,the mesas and ring are polished. A soft polish process may be performedto polish the mesas. The soft polish may at least partially polish wallsof the mesas as well as the tops of the mesas.

In method 500 the protective ceramic coating was deposited prior todeposition of the mesas and ring. However, in alternative embodimentsthe mesas and ring may be deposited prior to the protective ceramiccoating, and the protective ceramic coating may be deposited over themesas. The protective ceramic coating may be highly conformal, and sothe shape of the mesas and ring may be unchanged after deposition of theprotective ceramic coating over the mesas and ring.

FIGS. 6A-C illustrate the deposition of a ceramic material through amask 610 to form circular mesas with rounded edges on a surface of anelectrostatic chuck 640. The mask 615 includes multiple holes 615. Inone embodiment, the mask is approximately 1-3 mm thick. In oneembodiment, the mask is approximately 2 mm thick. In one embodiment, theholes are circular holes having a diameter of approximately 0.5-3 mm. Inone embodiment, the holes have a diameter of about 0.5-2 mm. In oneembodiment, the holes have a diameter of about 1 mm. In one embodiment,the holes are equally sized. Alternatively, the holes may have differentdiameters. In one embodiment, the holes have an aspect ratio of 1:2 to2:1 width to height.

As illustrated, in some embodiments the holes have flared top ends 620and flared bottom ends 625. The flared ends may have a diameter that isapproximately 30-70% larger than a diameter of the holes at a narrowestregion of the holes (e.g., centered vertically in the hold). In oneembodiment, the flared ends have a diameter that is approximately 50%larger than the diameter of the holes at the narrowest region. The topends and the bottom ends may have flares of the same shape and size.Alternatively, the top ends may have flares of different sizes and/orshapes than the flares at the bottom ends.

The mask 610 is placed over the electrostatic chuck 640, which includesa protective ceramic layer 635 that has been deposited onto a surface ofthe electrostatic chuck 640. In FIG. 6A, small mesas 630 with roundededges have been deposited. In FIG. 6B, deposition has continued, and thesmall mesas 630 have become larger mesas 631 with rounded edges. In FIG.6C, the deposition has continued to completion, and the mesas 632 havereached their final size. Notably, the mesas 632 do not contact thewalls of the holes 615 because of the flared bottom ends 625.

FIG. 7 illustrates a top view of a mask 710 used to form mesas and aring on a ceramic body 705 of an electrostatic chuck, in accordance withone embodiment. As shown, the mask 710 is a negative mask that has afirst diameter that is less than a second diameter of the ceramic body705. Accordingly, a deposition process may cause a ring to form at theperimeter of the ceramic body where the ceramic body is not covered bythe mask 710. The mask 710 additionally includes many holes 715. Thedeposition process causes a mesa to form at each of the holes 715.

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent invention. It will be apparent to one skilled in the art,however, that at least some embodiments of the present invention may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentinvention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” When the term “about” or “approximately” is usedherein, this is intended to mean that the nominal value presented isprecise within ±10%.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner. In one embodiment, multiple metal bondingoperations are performed as a single step.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. An electrostatic chuck comprising: a ceramic bodycomprising an embedded electrode; a first ceramic coating on a surfaceof the ceramic body, wherein the first ceramic coating fills pores inthe ceramic body; a second ceramic coating on the first ceramic coating;and a plurality of mesas on the second ceramic coating, the plurality ofmesas having rounded edges.
 2. The electrostatic chuck of claim 1,wherein the ceramic body comprises a material from the group consistingof AlN, TiO, TiN, SiC and Al₂O₃.
 3. The electrostatic chuck of claim 1,wherein the second ceramic coating comprises a material from the groupconsisting of Al₂O₃, AlN, Y₂O₃, Y₃Al₅O₁₂ (YAG), and AlON.
 4. Theelectrostatic chuck of claim 1, wherein the second ceramic coatingcomprises an amorphous ceramic comprising Yttrium, Aluminum and Oxygen,wherein at least 8% of the amorphous ceramic is Yttrium.
 5. Theelectrostatic chuck of claim 1, wherein the second ceramic coatingcomprises a rare earth oxide comprising Y₂O₃.
 6. The electrostatic chuckof claim 1, wherein the plurality of mesas have an average surfaceroughness of about 2-12 micro-inches.
 7. The electrostatic chuck ofclaim 1, wherein the plurality of mesas each comprises a material fromthe group consisting of Al₂O₃, AlN, Y₂O₃, Y₃Al₅O₁₂ (YAG), and AlON. 8.The electrostatic chuck of claim 1, wherein the second ceramic coatinghas an average surface roughness of about 2-12 micro-inches.
 9. Theelectrostatic chuck of claim 1, wherein the second ceramic coating has athickness of about 5-30 microns.
 10. The electrostatic chuck of claim 1,wherein the first ceramic coating comprises AlN or Al₂O₃.
 11. Theelectrostatic chuck of claim 1, wherein the first ceramic coating has anaverage surface roughness of about 4-10 micro-inches.
 12. Theelectrostatic chuck of claim 1, wherein the plurality of mesas aredeposited mesas that lack sharp edges.
 13. The electrostatic chuck ofclaim 1, further comprising a deposited ring on the second ceramiccoating at a perimeter of the ceramic body, wherein the deposited ringcomprises a material selected from the group consisting of Al₂O₃, AlN,Y₂O₃, Y₃Al₅O₁₂ (YAG), and AlON.
 14. An electrostatic chuck comprising: aceramic body comprising an embedded electrode; a first ceramic coatingon a surface of the ceramic body, wherein the first ceramic coatingfills pores in the ceramic body; a plurality of mesas on the firstceramic coating, the plurality of mesas having rounded edges; and asecond ceramic coating that covers the first ceramic coating and theplurality of mesas.
 15. The electrostatic chuck of claim 14, wherein thefirst ceramic coating comprises a first material selected from the groupconsisting of AlN and Al₂O₃.
 16. The electrostatic chuck of claim 15,wherein the second ceramic coating comprises a second material selectedfrom the group consisting of Al₂O₃, AlN, Y₂O₃, Y₃Al₅O₁₂ (YAG), and AlON.17. The electrostatic chuck of claim 16, wherein the plurality of mesaseach comprise the first material or the second material.
 18. A circularmask comprising: a body; and a plurality of through holes in the body,the plurality of through holes having an aspect ratio of approximately1:2 to approximately 2:1, wherein at least one hole of the plurality ofthrough holes comprises a flared top end and a flared bottom end,wherein the flared top end is to funnel particles through the at leastone hole onto an electrostatic chuck to form a mesa on the electrostaticchuck, wherein the flared bottom end prevents the mesa from contactingthe circular mask.
 19. The circular mask of claim 18, wherein thecircular mask has a thickness of approximately 1-3 mm.
 20. The circularmask of claim 18, wherein the flared top end and the flared bottom endeach have a first diameter that is approximately 20-70% greater than anarrowest region of the at least one hole.